Acro problem :(

[Corona007]

Hey guys,
So I have had this acro for about 3 months but the last 3 weeks the bottom looks to be turning black.
My tank is mixed with seratosa, slimer, monti cap along with LPS and everyone looks great.
2 clowns and a gobi 20 gal tank.
Sg 1025, ph 8.0-8.2, hk 10.5, ca 400, mg 1300, po .03-.05, temp 76-82

Anyone have a clue please chime in.
Thx.

http://[URL=http://s217.photobucket.com/user/corona007_photo/media/Reef%20tank/image_zpszlxsqayg.jpeg.html]

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[nuvuku]

Just from a glance your parameters look ok but your temp really should not swing from 76-82. What kind of temperature reading device are you using? If it is swinging that much I would try to get it to 77-78. Also can you describe the black gunk more?

 

[Corona007]

It's a cobalt heater that I use as a thermometer. It displays current temp and where it suppose to be. I had a fan on top that kept it under 80 on warm days but didn't think it would have any detrimental effects on the corals. So I don't run it anymore.

The black stuff is not slimie, just seems to be turning that black color on the base.
What I don't get is everyone else looks great.
Oh, and my no3 is <5 forgot the mention that.

Thanks for the response, I've tried googling but can't seem to find anything like it.

 

[DaveRaz]

Persoannly I woukdnt trust that heater internal thermometer.